Pneumatic-spring wheel-suspension leg

ABSTRACT

A pneumatic-spring wheel-suspension leg for motor vehicles. The leg comprises a bellows ( 1 ) that can be rolled up over a jacket ( 3 ) and accommodates a pneumatics chamber ( 9 ), a hydraulic dashpot inside the bellows or jacket, and a piston rod ( 5 ) that travels into and out of the dashpot and is attached axially and resiliently directly or indirectly at one end to the vehicle&#39;s chassis. The object is to relieve the dashpot of difficult attenuation tasks when a hard wheel suspension is necessary. The leg accordingly includes another pneumatics chamber ( 10 ) and the communication between the two pneumatics chambers can be partly or entirely blocked by a valve.

[0001] The present invention concerns a pneumatic-spring wheel-suspension leg as recited in the preamble to claim 1. Such legs are particularly employed in smoothly suspended vehicles. A device of this genus is disclosed in German 19 819 642 A2. The “spring” is essentially a bellows with connections and attachments at one end and accommodating a hydraulic oscillating dashpot. One end of the dashpot extends out of the bellows and is also provided with connections and attachments.

[0002] To adapt its performance curve or degree of attenuation to the vehicle's operation in terms of road conditions, speed, and other parameters, the dashpot is provided with controls. Controls are especially necessary when the road is very rough, powerfully kicking the wheels out. To ensure satisfactory adhesion of the wheels to the road accordingly, the suspension's performance curve must be as hard as possible. In pneumatically sprung vehicles in particular, which must have as soft a suspension as possible, this means that the dashpot must have as wide a range of controls as possible on the other hand, which can lead to complicated designs with a density of controls. The object of the present invention is a pneumatically sprung wheel-suspension leg of the aforesaid genus that can be relieved of difficult attenuation tasks when a hard wheel suspension is necessary.

[0003] This object is attained in accordance with the present invention as recited in the body of claim 1. Claims 2 through 12 address practical alternative and advanced embodiments.

[0004] The advantages of the present invention are that the spring's performance curve can also be varied between soft and hard, whereby the curve switches automatically to hard when the wheel kicks out considerably toward the vehicle's body and to soft once the wheel has mostly stopped executing such long-wave motions.

[0005] One embodiment of the present invention will now be specified with reference to the accompanying drawing, wherein

[0006]FIG. 1 is a longitudinal section through a pneumatic-spring wheel-suspension leg and

[0007]FIG. 2 a larger-scale depiction of the top portion of FIG. 1.

[0008] Pneumatic-spring wheel-suspension legs preferably include a pneumatic spring that accommodates a hydraulic dashpot. As will be evident from FIG. 1, the spring essentially comprises a bellows 1 hermetically sealed off at one end from a pneumatic cylinder 2 and at the other from a fastener that attaches the spring to a vehicle's chassis. The end of bellows 1 adjacent to the dashpot extends inward by way of a roll-off jacket 3 and outward by way of a cylindrical holder 4. The dashpot consists of a cylinder 2 and of a piston rod 5 that travels into and out of it. At the end of the rod is a suspension bell 6 that is connected on the outside and preferably axially resilient to a supporting cylinder 8 by way of a rocker 7. Bell-supporting cylinder 8 is appropriately attached to an unillustrated location on the chassis.

[0009] Essentially above rod-suspension bell 6, bellows 1 accommodates two pneumatics chambers 9 and 10. Chamber 10 is invariable in volume and is essentially supported by cylinder 8. It extends into and out of the supporting cylinder and is surrounded by a solid jacket 11. Chambers 9 and 10 are charged with gas through a valve 12 inside bell-supporting cylinder 8.

[0010] Pneumatics chambers 9 and 10 can be partly or entirely blocked off from each other by a particular valve, depicted in larger scale in FIG. 2. This valve includes a gasket 13, fastened in the illustrated example directly to bell-supporting cylinder 8 and hence indirectly to the vehicle's chassis. The valve is provided with sealing ridges on each surface. The ridges in the present example are in the form of resilient lips 14, 15, and 16 arrayed in a circle. The upper lips, 14 and 15, demarcate an annular gap. Contact surfaces 19 and 20 are provided at specific distances 17 and 18 from lips 14, 15, and 16. These contact surfaces are fastened to the end of the piston rod. The upper contact surface, 19, is represented by the base of rod-suspension bell 6. The lower contact surface, 20, is a disk resting at the end of piston rod 5 above a compression-limiter buffer 21.

[0011] With the pneumatic-spring leg out of operation, the valve will remain in the state represented in FIG. 2. Distances 17 and 18 are approximately equal. The valve communicates with pneumatics chamber 10 by way of bores 22 and 23 extending through bell supporting cylinder 8 and rod-suspension bell 6. The two chambers can accordingly freely exchange fluid as long as the leg is out of operation.

[0012] Due to the axially resilient suspension of piston rod 5 from rocker 7, the rod, and with it contact surfaces 19 and 20, will move either up or down depending on how powerfully piston rod 5 is resting against bell-supporting cylinder 8 and hence against the chassis. Simultaneously, depending on the direction of force, one of distances 17 and 18 will decrease until a lip 14, 15, or 16 comes to rest against a contact surface 19 or 20, closing the associated valve. In this situation only pneumatics chamber 9 will still be acting as a spring, and the performance curve will be hard. The hardness will ensure reliable roadway contact.

[0013] Once the wide relative motion between the wheel and the chassis ceases, the channel between pneumatics chambers 9 and 10 will be more or less opened again.

[0014] Lips 14, 15, and 16 can vary in shape. They can, as illustrated, be in the form of beads or be provided with ridges. They can also exclusively or in supplement to other components act as compression or tension limiters. They can be varied in shape to establish a performance curve. Alternatively however, compression limiter buffer 21 can also be involved in controlling the valve by, as it comes into contact with the dashpot, supporting the decrease in distance 18.

[0015] The action of the valve can also be varied by varying the shape and/or hardness of rocker 7. This component can be of a resilient material. It can even be a metal spring, a cup spring for instance. Combinations are also possible.

[0016] The pneumatics chambers and valve can also differ in form and position. The valve in particular can be kinematically reversed, with gasket 13 fastened to piston rod 5. In this event of course, contact surfaces 19 and 20 will be fastened to the vehicle's chassis.

List of Parts

[0017]1. bellows

[0018]2. cylinder

[0019]3. roll-off jacket

[0020]4. cylindrical holder

[0021]5. piston rod

[0022]6. rod-suspension bell

[0023]7. rocker

[0024]8. bell-supporting cylinder

[0025]9. pneumatics chamber

[0026]10. pneumatics chamber

[0027]11. jacket

[0028]12. valve

[0029]13. gasket

[0030]14. seal-creating edge (lip)

[0031]15. seal-creating edge (lip)

[0032]16. seal-creating edge (lip)

[0033]17. distance

[0034]18. distance

[0035]19. contact surface

[0036]20. contact surface

[0037]21. compression-limiter buffer

[0038]22. communicating bore

[0039]23. communicating bore 

1. Pneumatic-spring wheel-suspension leg for motor vehicles comprising a bellows (1) that can be rolled up over a jacket (3) and accommodates a pneumatics chamber (9), a hydraulic dashpot inside the bellows or jacket, and a piston rod (5) that travels into and out of the dashpot and is attached axially and resiliently directly or indirectly at one end to the vehicle's chassis, characterized in that the leg includes another pneumatics chamber (10) and in that the communication between the two pneumatics chambers can be partly or entirely blocked by a valve.
 2. Pneumatic-spring leg as in claim 1, characterized in that the valve can close more or less extensively independently of how forcefully the piston rod (5) is resting against the vehicle's chassis.
 3. Pneumatic-spring leg as in claim 2, characterized in that the valve will remain entirely open as long as the piston rod (5) is not exerting any force against the chassis.
 4. Pneumatic-spring leg as in claim 2, characterized in that the valve will remain closed as long as the piston rod (5), traveling in either direction, is exerting a prescribed force against the chassis.
 5. Pneumatic-spring leg as in one or more of claims 1 through 4, characterized in that the valve is controlled in accordance with the relative motion between the piston rod (5) and the chassis.
 6. Pneumatic-spring leg as in one or more of claims 1 through 5, characterized in that one pneumatics chamber (9) is essentially positioned below the end of the piston rod (5) and the other pneumatics chamber (10) essentially above the end of the piston rod.
 7. Pneumatic-spring leg as in one or more of claims 1 through 6, characterized in that the volume of fluid in one pneumatics chamber (10) remains constant.
 8. Pneumatic-spring leg as in one or more of claims 1 through 7, characterized in that the valve includes a gasket (13) with edges (14, 15, & 16) on each side that create a seal in conjunction with elevated contact surfaces (19 & 20) located at specific distances therefrom.
 9. Pneumatic-spring leg as in claim 8, characterized in that the gasket (13) is fastened to a component of the vehicle's chassis or to the piston rod (5) and the contact surfaces (19 & 20) are fastened to the piston rod or to a component of the vehicle's chassis.
 10. Pneumatic-spring leg as in one of claims 8 and 9, characterized in that the seal-creating edges (14, 15, & 16) are resilient, preferably rubber or plastic, lips.
 11. Pneumatic-spring leg as in one or more of claims 1 through 10, characterized in that the seal-creating edges (14, 15, & 16) also act as mechanical compression or tension limiters.
 12. Pneumatic-spring leg as in one or more of claims 1 through 11, characterized in that the decrease in the distance (18) between one seal-creating edge (16) and its associated contact surface (20) is assisted by the compression-limiter buffer (21) as the dashpot comes to rest against the latter. 